John Calvin Commentary Deuteronomy 11:16

"Take heed to yourselves, lest your heart be deceived, and ye turn aside, and serve other gods, and worship them;" — Deuteronomy 11:16 (ASV)

Take heed to yourselves. By often emphasizing the same thing, namely, that they should diligently take heed, he indirectly arraigns humanity’s proneness to superstition. This is also expressed again in the words, that your heart be not deceived, for by these words he signifies that unless they take diligent heed to themselves, nothing will be easier than for them to fall into the snares of Satan.

Therefore, the impudence of the Papists is all the less excusable, as they intoxicate their own and others’ minds with a false sense of security, when God constantly exhorts them to vigilance. Let us learn, then, that since many impostures and deceits besiege us on every side, we, in the vanity of our nature, are immediately liable to fall into them unless we carefully guard ourselves.

By the expression “turn aside,” he implies what has been said before: that whoever strays into corrupted worship impiously falls away from the true God. Unbelievers hardly think so, for to them it is a light transgression to go too far in this respect. They would willfully try to blind the eyes of God with their inventions; indeed, there is nothing too silly that they would not desire God to approve and sanction.

But if it is objected that obedience is better than sacrifice, they shield themselves with their good intention, as if God were not at liberty to repudiate what they foolishly impose upon Him. At any rate, they so stubbornly indulge in their thoughtless zeal that they will hardly acknowledge the slightest fault in it.

But, on the other hand, God declares that all are apostates who do not confine themselves to the simplicity of the Law. A threat is again added: that God will avenge the violation of His worship and will curse their land until He destroys them by severe scarcity and famine. Finally, He pronounces that they shall perish from that land which God had promised them so that He might be purely worshipped there.